<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>underscore</title>
</head>
<body>
<script src="underscore.js"></script>
<script type="text/javascript">
   var test=_.map([1, 2, 3], function(num){ return num * 3; });
   console.log(test)
</script>
</body>
</html>